Alarm-fuse for telephone-exchanges.



PATENTED APR. 17, 1906.

INo. 817,959.

E. B. CRAFT. ALARM FUSE FOR TELEPHONE EXCHANGES.

APPLICATION FILED FEB-5,1904.

UNITED sTATEs PATENT oEEIcE.

EDWARD B. CRAFT, OF CHICAGO,

ELECTRIC COMPANY, OF ILLINOIS.

ILLINOIS, ASSIGNOR TO \VESTERN CHICAGO, ILLINOIS, A CORPORATION OF Specification of Letters Patent.

Patented April 17, 1906.

Application filed February 5,1904. Serial No. 192,183.

To (LZZ zt'hmn 7'2 may concern.-

Be it known that I, EDWARD B. CRAFT, a

citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Alarm-F uses for Telephone- Exchanges, of which the following is a full, clear, concise, and exact description.

My invention relates to that class of protective devices which are used very generally es in order to. guard the I in telephone-exchan apparatus against a normal currents which may be produced accidentally or otherwise.

In centralized energy systems it has been common to place fuses in the wires leading from the common battery to the different cord-circuits. These fuses have been mounted close together in an upright position upon slate panels, one terminal of a given fuse being connected with the common battery busbar and the other terminal of the same fuse being connected with the wire leading to a particular cord-circuit or a group of cordcircuits. These protective devices are inconspicuous, being, say, one and three fourths inches long and three-oi hth of an inch wide. It is desirable that w en one of the fuses is blown the fact be readily ascertained by simple inspection.

My invention contemplates a protecting device comprising an insulating-mounting havin terminal pieces at the ends thereof, to one 0 which terminals is secured a sprin such as a coiled spring, the spring being pre f erably mounted upon a'suitable supporting member carried by such terminal piece. The spring is arranged to be held under tension by a fuse-wire, preferably of German silver, which completes the electrical connection between the terminal pieces, being connected with the terminal piece opposite that to which the spring is secured. The spring carries a target, preferably tubular and of glass of distinctive color, which is main-' tained by the s ring When under tension in a position such tiat it will be inconspicuous, the target bein carried by the spring upon the parting of tie fuse into a position of'dis- P y- The protective device embodying this in-.

ably employed, may be carried upon an angular portlon of an extension-arm of the spring, 7 so that when the spring is under tension the small end only of the target will be visible; but when the spring is released by the blowing of the fuse the target will be moved into a position such that the surface or side of the 5 target will be brought into View, thus making a very efficient signal and one that will be easily noticed.

My invention will be more readily understood by reference to the accompanying drawings, wherein I Fi ure 1 is a perspective view illustrating a I num er of protective devices embodying my I invent-ion mounted upon a fuse-panel. Fig. 2 is a sectional view on line 2 2 of Fig. 1.

The same letters of reference are used to designate like parts in both figures.

The slate panel a, which supports the pro- I tective devices, carries two bus-bars b c. The bus-bar I) would in practice be connected with one pole of the central-ofiice battery and is therefore termed the battery busy bar. The bus-bar 0 would be connected with the other pole of the central-office battery or the opposite pole of a local-alarm battery and include in its circuit an alarmsignal, such as an electric bell 0r lamp adapted to be displayed when a fuse is blown and the alarm-circuit completed. This bus-bar is therefore desi nated the alarm bus-bar. A number of olts or studs (2 12 extend l throu h the panel a and may each be conl necte with a conductor leading to a given cord-circuit or 1' sired. i The body portion or frame of the protective device E consists of an insulating-mounting e, carrying at the ends thereof terminal plates e e The terminal plate 6 carries a supporting member or arm, preferably a right-angled extension or plate e A coiled spring f is mounted upon the supportingl plate e and one end secured thereto by soldering or otherwise. The other end of said spring forms an arm f, which extends for some distance above the insulating-strip and carries a target g, which may be a tubular glass bead. The target which I have used l in practice consists of an opaque glass bead 2 of distinctive color, preferably white. The portion f of the army" upon which the tar group of cord-circuits, as de get is mounted is preferably bent at the angle, as shown, so that the target when in its normal position may be as inconspicuous as possible. As the panel a is in practice disposed in a vertical plane,.the small end only of the target would thus be seen when the spring is under'tension.

A tension-spring h of usual construction is connected with the terminal 6 and extends underneath the insulating-strip e and parallel therewith to a point above the alarm busbar 0. The fuse-wire i, which may be of German silver, connects the end of spring h with the extension-armf of the coiled spring and serves to maintain bot-h springsf h under tension. The fuse-wire i is preferably connected with the arm f at a point between the coil and the target. With this arrangement the target-carrying portion is rendered entirely independent of the fuse-wire, so that the frame and target are undisturbed by the blowing of the fuse and a new fuse may be easily substituted, and, in addition, the target is given a wide range of movement when released.

The protective device E is adapted to be mounted upon the panel a and the terminals e e thereof suitably secured to the bolt (1 and battery bus-bar b, respectively, preferably by binding-screws passing through notches in said terminals.

When the fuse-wire i is parted, the springs f h are released. The coiled spring in retracting moves. the target 9 into a position of display, as shown at the right in Fig. 1, the entire side or surface of the target coming into view, and the tension-spring h moves into engagement with the alarm bus-bar c.

It will be observed that the target-fuse is adapted to be readily removed from the supporting-plate upon which it is mounted and new parts substituted therefor. These removable parts, comprising the fuse-wire,

spring and target, are conveniently kept in stock, so that when any fuse is blown a new target-fuse may be readily substituted.

It is obvious that the alarm-fuse of my invention may be employed in the protection of circuits other than those particularly described in the foregoing. It is Well adapted for use with telephone-line circuits, where it is customary to roup the fuses of a number of lines in a smalfspace.

Having thus described my invention, I claim 1. A protective device comprising an insulating mounting-strip and terminal plates therefor, a spring secured to one of said terminals, a fuse-wire electrically connected with the other terminal and united with said spring to maintain the same under tension, and a target carried by said spring, said spring when under tension holding said target in an inconspicuous position, but being arm between the target and coil to maintain said spring under tension, said arm being adapted to be moved by the spring to bring the target into a position of display when the fuse-wire is parted.

3. A protective device comprising an insulating mountingstrip and terminal plates therefor, a spring secured to one of said terminal plates, a fuse-wire completing the electrical connection between said plates, and maintaining the spring under tension, an arm carried by said spring, and a tubular glass target carried by an angular portion of said arm, said arm when the spring is under tension maintaining the target inconspicuous, and being adapted upon the parting of the fuse to move said target into a position of display.

4. A protective device comprising an insulating mounting-strip e and terminal pieces 6 e therefor, a coiled spring f, a support e therefor, one end of said spring being electrically connected with the terminal 6, an extension-arm f formed by the other end of said spring, an opaque glass target g of distinctive color carried by an angular portion f of said arm, and a fuse-wire f maintaining said spring under tension and electrically connected with the terminal plate 6 said fusewire being united with the arm f between the target and coil whereby when the fuseis parted the target is moved into a position of display by the recoil of said spring.

- 5. A protective device comprising an insulating supporting-strip, terminal plates carried at the ends thereof, a coiled spring, a metallic supporting plate for said spring mounted upon one of said terminal plates at right angles thereto, one end of said spring being secured to said plate, an extension-arm carried by the other end of said spring, a leafspring secured at one end to the other terminal plate and extending parallel to the insulatingstrip on the side thereof opposite said coiled spring, a fuse passing through said strip and connecting said leaf-spring and extension-arm to maintain the coiled spring under tension, and a target of distinctive color carried by an angular portion of said extension-arm and adapted to be moved into a poparted.

and a target carried by an angular an insu- V 6. A protective device comprisin ates carlating sup orting-stri terminal ried at the ends there df, a coiled s pring supported by one of said plates, one end ofsaid spring being connected with said plate, an extension-arm carried by the other end of said spring, a leaf-spring connected with the other terminal plate and extending parallel to said insulating-strip on the side thereof op osite said coiled spring, a fuse passing through said strip and connecting the ends of said springs to maintain the coiled spring under tension,

ortion of said extension-arm independent 0 the current-carrying portion thereof, said target being adapted to be moved into a position of display by said arm when the fuse'is parted.

7. A protective device adapted to be mounted in a vertical plane, comprising an insulating supporting-strip, terminal plates carried at the ends thereof, a coiled spring supported by one of saidplates, one end of said spring being connected with said plate, an extension-arm carried by the other end of said spring, a portion of said arm being bent to lie at right angles, a fusewire electrically connected with the other terminal plate and united with said extension-arm between the angular portion thereof and the coiled spring to maintain said spring under tension, and a tubular target carried by said angular portion and normally maintained in an inconspicuous position with its small end alone visible, sald target being adapted to be moved by said arm to display its side surface when the fuse is parted.

In witness whereof I hereunto subscribe my name this 2d day of February, A. D. 1904.

EDWAR'D B. CRAFT.

Witnesses:

W. W. LEACH, ALFRED H. MOORE. 

